1. Field of the Invention
The present invention relates to a keyboard device suitable as an input/output device for use in a word processor, personal computer, or the like.
2. Description of the Related Art
FIG. 6 illustrates a keyboard device used as an input/output device. In this keyboard device, switch elements are constructed by placing a flexible insulating substrate 51, having a circuit (not shown) formed thereon, onto an insulating substrate 50 on which a conductor (not shown) is formed.
Each supporting member 52 is made of a synthetic resin in such a manner so as to include: a holding element 52a having a hole; a holding element 52c having a sliding slot 52b; and a cut-away part 52d formed between the holding elements 52a and 52c. These components are combined into a single supporting member 52. A plurality of similar supporting members are produced and placed on the insulating substrate 51.
First and second levers 53 and 54 are connected to each other via a shaft 55 such that they cross each other, wherein one end of the first lever 53 is slidably fit into the sliding slot 52b and one end of the second lever 54 is pivotably fit into the holding element 52a.
Each keytop 56 is made up of a synthesis resin in such a manner as to include: a holding element 56a having a hole and a holding element 56c having a sliding slot 56b wherein the holding elements 56a and 56c are disposed on the back surface of each keytop 56. The other end of the first lever 53 is pivotably fit into the holding element 56a and the other end of the second lever 54 is slidably fit into the holding element 56c thereby fixing the keytop to the first and second levers 53 and 54.
Dome-shaped elastic members 57 made of electrically insulating rubber are placed on the insulating substrate 51 in such a manner that they are located in the cut-away parts 52d of the respective supporting members 52. The top portion 57a of each elastic member 57 is in contact with the central crossing part of the first and second levers 53 and 54.
A plurality of key units each consisting of first and second levers 53 and 54, a keytop 56 fixed to the levers 53 and 54, and an elastic member 57 are disposed on the switch elements along a plurality of lines.
In the keyboard device constructed in the above-described manner, if a certain keytop 56 is pressed, the first and second levers 53 and 54 rotate about the shaft 55 and also pivot at their one end fit in the holding elements 52a and 56a, respectively. The other end of the first lever 53 slides in the sliding slot 52b and the other end of the second lever 54 slides in the sliding slot 56b. Thus, the first and second levers 53 and 54 move downward. As a result, the keytop 56 also moves downward while maintaining itself horizontal. As a result of the downward movement of the first and second levers 53 and 54, the top portion 57a of the elastic member 57 is pressed by the central crossing part 58 of the first and second levers 53 and 54, and finally the dome-shaped elastic member 57 is inverted in shape. As a result, the insulating substrate 51 is pressed by the elastic member 57 and the corresponding electric contact formed on the insulating substrate 51 comes in contact with the conductor disposed on the insulating substrate 50. Thus, a corresponding switch element is turned on.
If the pressing force against the keytop 56 is removed, the first and second levers 53 and 54 and the keytop 56 are pushed back by the elastic force of the elastic member 57 to their original positions where they were located before being pressed. The pressure by the elastic member 57 against the insulating substrate 51 is released and the insulating substrate 51 returns to its original position by its own restoring force. As a result, the contact with the conductor on the insulating substrate 50 is released and thus the switch element is turned off.
In the conventional keyboard device described above, since the dome-shaped elastic members 57 for actuating the corresponding switch elements are disposed between the insulating substrate 51 and the central crossing parts 58 of the first and second levers 53 and 54, the height H of the upper surface of the keytop relative to the insulating substrate 51 becomes great, and thus it is difficult to achieve a thin keyboard device.
Furthermore, since the elastic members 57 are simply placed in the cut-away parts 52d of the supporting members 52 on the insulating substrate 51, when the first and second levers 53 and 54 are attached to the supporting members 52 after the elastic members have been placed, the elastic members 57 move from their right position. Therefore, it is required to correct the position of the elastic members 57, and thus the assembling process is inefficient.
Furthermore, in the conventional keyboard device, it is required to modify the height H in accordance with specific applications. To this end, it is required to prepare various sizes of components including supporting members 52, first and second levers 53 and 54, and keytops 56. This causes an increase in cost, and makes it impossible to standardize the components. As a result, it is impossible to assemble the components into a keyboard device in an efficient manner.